https://www.geek.com/news/it-rains-iron-on-only-one-side-of-this-exoplanet-1820161/?source

This illustration shows a night-side view of the exoplanet WASP-76b (via ESO/M. Kornmesser)

Even the sturdiest umbrella wouldn’t withstand the rain on exoplanet WASP-76b.

Researchers using the European Southern Observatory’s Very Large Telescope (VLT) have observed an extreme world where it appears to bucket down iron.

“One could say that this planet gets rainy in the evening, except it rains iron,” lead study author David Ehrenreich, a professor at the University of Geneva, said in a statement.

The phenomenon, described in a paper published this week by the journal Nature, occurs because the planet, known as WASP-76b, only ever shows one face—the “day side”—to its parent star. The opposite “night side” remains in perpetual darkness.

Located some 640 light-years away in the constellation Pisces, the giant’s ultra-hot day side reaches temperatures above 4,350 °F—so hot that molecules separate into atoms and metals like iron evaporate into the atmosphere.

This comic-book-style illustration by Swiss graphic novelist Frederik Peeters shows a close-up view of the evening border of the exoplanet WASP-76b (via Frederik Peeters)

“A fraction of this iron is injected into the night side owing to the planet’s rotation and atmospheric winds,” astrophysicist Maria Rosa Zapatero Osorio, chair of the ESPRESSO science team, explained. “There, the iron encounters much cooler environments, condenses, and rains down.”

WASP-76b also has distinct day-night chemistry, according to the study.

Employing the new ESPRESSO instrument on ESO’s VLT in the Chilean Atacama Desert, astronomers identified chemical variations for the first time on an ultra-hot gas giant.

Specifically, they detected a strong signature of iron vapor at the evening border that separates the planet’s two hemispheres.

“Surprisingly, however, we do not see the iron vapor in the morning,” Ehrenreich said, likely because “it is raining iron on the night side of this extreme exoplanet.”

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